Utility Meter Accuracy - Home Energy Pros2016-12-09T15:51:21Zhttp://homeenergypros.lbl.gov/forum/topics/utility-meter-accuracy?commentId=6069565%3AComment%3A89877&feed=yes&xn_auth=noFor Rod, second part...
When…tag:homeenergypros.lbl.gov,2015-11-30:6069565:Comment:1927702015-11-30T03:48:45.554ZDennis Heidnerhttp://homeenergypros.lbl.gov/profile/DennisHeidner
<p>For Rod, second part...</p>
<p>When I see really large electric services... my first reaction my be "what a waste", but when I stop and catch my breath and take the time to ask why... something more useful is generally discovered. </p>
<p>My house is roughly 2800 sqft. Family of four... Seattle has a reasonably moderate marine climate. NM can be hot (but they don't have the air conditioning - per your comments), the summer time use is high and it looks like their loads are for a…</p>
<p>For Rod, second part...</p>
<p>When I see really large electric services... my first reaction my be "what a waste", but when I stop and catch my breath and take the time to ask why... something more useful is generally discovered. </p>
<p>My house is roughly 2800 sqft. Family of four... Seattle has a reasonably moderate marine climate. NM can be hot (but they don't have the air conditioning - per your comments), the summer time use is high and it looks like their loads are for a predominantly heating climate. But why 300A or 400A service.... that's isn't necessarily a "given" for that size of a house a 200A would likely be more than sufficient. So see if they know why the large electric service was installed... is there a sub panel that it is feeding... with stuff that was missed. If the house was older (mine was a 60's vintage)... maybe there are lots of lights... I had counted 110+ lights in my house... even with only 55 on at a time... that's a big load.</p>
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<p>Our house originally had a 125A service panel with about 20 circuits. When we went through the house about eight years ago.. I moved to a 200A service panel with 40 circuits. But then immediately had the main breaker downgraded to a 150A breaker. That panel feeds a 100A sub panel via an automatic transfer switch for the generator. That sub panel has lots of smaller circuits in it... typically 15A circuits. Seems convoluted but I wanted to be able to measure and monitor individual circuits... and I didn't like the old system in which if a breaker tripped nearly all the lights on one floor in the house would go dark. We chose to break up lots of big circuits into many smaller circuits. (and in case anyone asks... yes it was permitted and inspected by electrical inspector and work was done by a licensed electrician). </p>
<p>The point being the easiest way for to get the many circuits was to use a larger panel... with the larger bus bar. You don't find 125A panels, or 150A panels with 40 circuits... so again... why the big service... was it just to have lots of circuits - with a few heavy swingers... or was it because the original owners had a kiln, a horse barn, etc.?</p>
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<p>Nowdays, if that same house with a large service was located in WA, OR, or perhaps CO... the question might be... how big are the grow lamps and fans... but at the same time - the house may have a family that likes to grow their own organic vegetables... tomatoes, carrots, peas, celery... and not the hemp products.. </p>
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<p>If the family are the original owners they might also be able to indicate if the consumption has stayed the same or climbed over the years... </p>
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<p>Also how many yard lights do they have? If this is out in the country... with kids - they may have added extra yard lights that go on after dark such that kids can play basketball on a court by the garage. If the yard lights are mercury vapor, halogen, etc... that could easily add up.... and switching those to LED's saves a large chunk.</p>
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<p>You might not be able to whittle away the 500kWh difference or 10kWh difference.... with lots of accurate measurements... it is often just to eyeball them and say... 400W x 8 hours a day *365 days = 1,100+ kWh... and you'll move that to a LED equivalent and save 700kWh/yr... it may cost less to fix the problem then to measure it.</p>
<p></p> Rod, I did see earlier that…tag:homeenergypros.lbl.gov,2015-11-30:6069565:Comment:1927692015-11-30T03:04:05.369ZDennis Heidnerhttp://homeenergypros.lbl.gov/profile/DennisHeidner
<p>Rod, I did see earlier that you had calculated the loads. The key is even though a consumer device may not have the accuracy... you can still use it to find the "phantom loads". You need to use that spread sheet of expected loads and try to place them on a circuit in the breaker panel... then it may be necessary to monitor &amp; move from circuit to circuit over a period of several days. You should see the culprit -- if you leave the data logging going long enough to catch the actual…</p>
<p>Rod, I did see earlier that you had calculated the loads. The key is even though a consumer device may not have the accuracy... you can still use it to find the "phantom loads". You need to use that spread sheet of expected loads and try to place them on a circuit in the breaker panel... then it may be necessary to monitor &amp; move from circuit to circuit over a period of several days. You should see the culprit -- if you leave the data logging going long enough to catch the actual problem. My guess is the phantom is not really going to be a small load... but it will be a big intermittent load . For example I've seen compressor stalls on HVAC systems going from where they were adding 2kW or 3KW average... to suddenly 6kW or 7kW average -- as the condenser motor had seized up.. and was having problems and the poor compressor was getting clobbered... A water pump thats leaking water back at the well - or even a water tank that has a failed rubber bladder and is short cycling the pump will consume a lot more power. </p>
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<p>Now back to that 10kWh anomaly a year...if the total use is 38,000kWh, 10% is 3800kWh, 5% is roughly 1800kWh/yr... then 0.3% is likely to be above 10kWh/yr... that 10kWh is well into the noise level for many of the best logging equipment -- when you consider the size of the load... in fact a reasonable error might be up around 100kWh/yr. </p>
<p>On the other hand if you expected 10kWh max loads a year and sized the measuring equipment for the smaller loads/current.. then the error might be around 30Wh (0.3% measuring accuracy)</p>
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<p>If the test equipment you are using is only rated at 3% accuracy... then it is reasonable to have a measurement error in the range of 1,100kWh/yr (roughly). That makes 500kWh/yr look pretty good...</p>
<p>I've gone through the process that you tried with the house... and you can indeed find all and accurately account for nearly every watt... if you are willing to take the time and pay the price to do so... it takes lots of data logging with many CT's sized appropriately for the circuit loads. The logged values can not be simply the hourly cumulative totals... or even the fifteen minute... you many need under minute measurements. Then you need not to get caught up in believing that the totals are precise -- they are generally not -- ESPECIALLY if you use the off the shelf consumer logging devices... TED's for example. You'd get a good feeling for the numbers but not precise.</p>
<p>I'd start looking at the 75A, 50A, 30A circuits first.... use CT's that appropriate for the circuit size and capture the data in second intervals if you can.... the small intervals will let you detect motor starts... etc. Then go through the 20A circuits and compare against the items on that circuit...</p>
<p>Then on to the 15A, etc...</p>
<p>My guess is before you hit the 20A circuits you'd find the big items that are causing the unexpected high loads during the summer time.... and for me... that keeps coming back to motors... most likely pumps or big fans (attic fans for example).</p>
<p>Since this is getting long I'll break response into multiple pieces.</p>
<p>As mentioned I've gone through this before... shrinking the equivalent (gas + electric) from about 54,000kWh down to under 18,000kWh (gas+electic). Note the (gas+electric) means the BTU heat value of the gas was converted to kWh and added to the consumption. That wasn't a 54MWh electric only consumption. But we shrank the electric the fastest... the gas usage is still slowly shrinking..</p>
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<p> </p> Dennis, that's a ton of usefu…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1928612015-11-29T21:29:17.117ZRodney Foxhttp://homeenergypros.lbl.gov/profile/RodFox
<p>Dennis, that's a ton of useful info and it will take me a bit to fully assimilate those articles/studies. I sure do appreciate your input. However, I'm disappointed to know that under low loads the inaccuracy will be in the favor of the homeowner rather than the utility. Makes perfect sense though.</p>
<p>I'm still in favor of having the utility company come out again to test their equipment, knowing what I know now. I want to pay close attention to exactly what they are testing this time to…</p>
<p>Dennis, that's a ton of useful info and it will take me a bit to fully assimilate those articles/studies. I sure do appreciate your input. However, I'm disappointed to know that under low loads the inaccuracy will be in the favor of the homeowner rather than the utility. Makes perfect sense though.</p>
<p>I'm still in favor of having the utility company come out again to test their equipment, knowing what I know now. I want to pay close attention to exactly what they are testing this time to be sure they check all components.</p>
<p>If you look at the original posting, you will see that I had done some exhaustive research into their loads and was able to account for everything. That total didn't match the utility company's numbers though, which is what set me off on this wild goose chase. At some point I will have reconciliation, but until then, I've sort of adopted this project for a learning experience, as it's important for me to know what's going on in that mysterious black box called a meter.</p>
<p>Thanks again for all the great research and information!</p> Yup.....
1200 amp service to…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1927662015-11-29T09:42:37.890ZBen Haashttp://homeenergypros.lbl.gov/profile/ben
<p>Yup.....</p>
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<p>1200 amp service to the compound..... 3 -400 amp panels, all single phase since 3 phase does not extend in that part of the valley...</p>
<p>To explain further... Jackson power is provided by a Co-Op.. Lower Valley Energy.. We all are part owners in it... Since most houses here are spread out, 99% of them have their own ground transformer, to cut down on secondary losses from long runs... And 95% of service here is underground...</p>
<p>Those transformers have 4 -200…</p>
<p>Yup.....</p>
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<p>1200 amp service to the compound..... 3 -400 amp panels, all single phase since 3 phase does not extend in that part of the valley...</p>
<p>To explain further... Jackson power is provided by a Co-Op.. Lower Valley Energy.. We all are part owners in it... Since most houses here are spread out, 99% of them have their own ground transformer, to cut down on secondary losses from long runs... And 95% of service here is underground...</p>
<p>Those transformers have 4 -200 amp taps inside... The mansion / compound I spoke of has three transformers enclosed in a large 6'X6'X5' cabinet.. Each feeding their own 400 amp panel /service...</p>
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<p>It would be hard for normal electricians to grasp the extent of excess the kazillionaires go to in this valley without you actually standing there and seeing it in real life... You guys would shake your head in disbelief...</p> The more I think about it if…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1925982015-11-29T04:43:39.328ZWalter Ahlgrimhttp://homeenergypros.lbl.gov/profile/WalterAhlgrim
<p>The more I think about it if the problem cannot be the current transformers reading small loads, any errors would most likely be in the customers favor not the unities.</p>
<p>There must be a load somewhere that is not off. Did you say no AC units were installed? Often the compressors have heaters that run continuously if the breaker is on.</p>
<p>Are there any swimming pools, generators, outdoor lighting or outbuildings on site?</p>
<p>The more I think about it if the problem cannot be the current transformers reading small loads, any errors would most likely be in the customers favor not the unities.</p>
<p>There must be a load somewhere that is not off. Did you say no AC units were installed? Often the compressors have heaters that run continuously if the breaker is on.</p>
<p>Are there any swimming pools, generators, outdoor lighting or outbuildings on site?</p> Note to readers 0.5A instead…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1925972015-11-29T03:38:10.873ZDennis Heidnerhttp://homeenergypros.lbl.gov/profile/DennisHeidner
<p>Note to readers 0.5A instead of 5A for reading with A/D.... the edit to correct that didn't apparently take because of timeouts... likewise 0.1A instead of 1Amp.. </p>
<p>Note to readers 0.5A instead of 5A for reading with A/D.... the edit to correct that didn't apparently take because of timeouts... likewise 0.1A instead of 1Amp.. </p> Rod,
I have some of the CT's…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1926512015-11-29T03:15:53.884ZDennis Heidnerhttp://homeenergypros.lbl.gov/profile/DennisHeidner
<p>Rod,</p>
<p>I have some of the CT's that you referenced in the openenergymonitor system. They are at "best" 3% devices... the openenergysystem is likely to have system error/uncertainty in/around 10%. The utility meters will be well under 2%.</p>
<p>The CR reference on digikey and the other references are for essentially generic CT's. As noted in the accuracy chart from the CR ansi reference... you can get a more accurate tolerance if the load (burden) resistor is a low value (and…</p>
<p>Rod,</p>
<p>I have some of the CT's that you referenced in the openenergymonitor system. They are at "best" 3% devices... the openenergysystem is likely to have system error/uncertainty in/around 10%. The utility meters will be well under 2%.</p>
<p>The CR reference on digikey and the other references are for essentially generic CT's. As noted in the accuracy chart from the CR ansi reference... you can get a more accurate tolerance if the load (burden) resistor is a low value (and precision). That's not the case in the little clamp on CT's with the openenergymonitor....</p>
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<p><a rel="nofollow" href="http://www.elstersolutions.com/assets/products/products_elster_files/ALPHA_Plus_meter_022008.pdf" target="_blank">http://www.elstersolutions.com/assets/products/products_elster_file...</a></p>
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<p>The link below is from a Navigant testing of smart meters a few years ago...</p>
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<p><a rel="nofollow" href="http://interchange.puc.state.tx.us/WebApp/Interchange/Documents/38053_17_662585.PDF" target="_blank">http://interchange.puc.state.tx.us/WebApp/Interchange/Documents/380...</a></p>
<p>Accuracy even for light loads (10% meter rating) is still well under 1%. The meters do not read high at lower loads... if anything they may read low. The CT linearity is still pretty good at the low end - but unless you pay a premium for the A/D to measure the voltage across the CT load (burden) resistor... the A/D is likely to be 12 bit... perhaps 16bits... at 12 bits that means the max reading is broken into 4096 smaller chunks. Roughly a 200A load would read near the value of 4000/4096... but anything smaller than a 5A load might read nearly the same.... consumer (non-utility grade) measuring equipment often only use a 12bit A/D, where as a utility would use at least a 16bit A/D and more accurate time references. with 16bits you can resolve down to roughly 1amp. I believe the utility meters use a chipset designed just for wattmeters and they may actually use a 20 bit A/D.... (TI chipset?)... </p>
<p>If you dig on the internet you can also find some of the testing laboratories analysis of the utility meters... and they often test the meters down to below 1 amp..... and see 0.3% accuracy or better for the very small loads.</p>
<p>Extrapolating the loads as you have done - is very prone to large errors... I doubt that you'll find a constant on load of 16Amps.... </p>
<p>However there are some areas which can really spike up and cause some strange errors.... coffee pots, instant hot water taps, and even the nice fancy bidet toilets with heated seats. Look for in floor electric heat of bathrooms. If you have a thermal imaging camera -- use it.</p>
<p>Also since these guys are on a well... do they also have a septic system.... one that perhaps requires a pump to move that valuable human byproduct up a hill to a drain field? I've seen that... large loads can also be caused by motors that are nearing their end of life and have some shorted windings... Build up a spread sheet of the expected loads and see if you can total them up... I've simply used the max rating on the appliance as an indicator and then look at those appliances to see their use profile and if there is a problem. (For example count the lightbulbs in the house - if incandescent multiply by 60W or 75W... add to spread sheet...) Clock radio's stereo's.. etc just add in 10W... you should be able to find some big stuff... and account for the circuits they are on.... </p>
<p>Look carefully at their radiant floor loops... are they using a lot of separate pumps for the circuits instead of valves? Each of those pumps can be a 500W+ load... and if there is a valve behind them constricting flow but the heating system hasn't told the pumps to stop... it will burn through a lot of power pumping nothing....</p>
<p>Old still plugged in refrigerator or freezer?... sometimes they get forgotten and are buried under piles of stuff in a garage...</p>
<p>Heat tape on water pipes that are still plugged in... perhaps even outside of the house going to an out building? And then there are the electric driveway and sidewalk de-icing systems... all easily seen this time of the year if you have a thermal imaging camera..............</p>
<p>How big is the yard? Are they watering the yard using well water? Do they have a big garden and they've been watering it also? It might be that the high summer use is related to water use... consider putting a CT on the pump circuit and just monitoring it for a while. You might discover that the water line from the pump itself up to the tank... is leaking in the well hole resulting in that water pump running a lot...(others suggested a pump problem)... it happens a lot as the pumps and/or poly pipe reach end of life....</p>
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<p></p> 1200A service... really? or…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1926502015-11-29T02:07:24.001ZDennis Heidnerhttp://homeenergypros.lbl.gov/profile/DennisHeidner
<p>1200A service... really? or did you mean 200A. That size service would likely result in its own large transformer (probably ground mounted)... and likely three phase to home.</p>
<p>The electrician likely did the audio/video system as well as a designer lighting system... neither would result in the need of a 1200A service... may be with hot tub, swimming pool, sauna, big air conditioners that might make it to 400A....</p>
<p>1200A service... really? or did you mean 200A. That size service would likely result in its own large transformer (probably ground mounted)... and likely three phase to home.</p>
<p>The electrician likely did the audio/video system as well as a designer lighting system... neither would result in the need of a 1200A service... may be with hot tub, swimming pool, sauna, big air conditioners that might make it to 400A....</p> That's great news! Guess that…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1926492015-11-29T01:03:50.606Ztedkiddhttp://homeenergypros.lbl.gov/profile/tedkidd
That's great news! Guess that means there are a bunch of blower doors getting used in Jackson finally!
That's great news! Guess that means there are a bunch of blower doors getting used in Jackson finally! Teton County and the Town of…tag:homeenergypros.lbl.gov,2015-11-29:6069565:Comment:1928582015-11-29T00:38:50.203ZBen Haashttp://homeenergypros.lbl.gov/profile/ben
<p>Teton County and the Town of Jackson Adopted the 2014 IRC energy code.... With that, inspectors now require blower door testing so caulking plates, outlets and any opening is almost needed to pass the test... Funny though..... I have been a contractor here for 25 years and in all structures I have built. I have caulked those joints for at least 20 years.... A case of good caulk bought at Jackson Lumber and a half day of my time works out to 300 bucks... Max.... And I always have happy…</p>
<p>Teton County and the Town of Jackson Adopted the 2014 IRC energy code.... With that, inspectors now require blower door testing so caulking plates, outlets and any opening is almost needed to pass the test... Funny though..... I have been a contractor here for 25 years and in all structures I have built. I have caulked those joints for at least 20 years.... A case of good caulk bought at Jackson Lumber and a half day of my time works out to 300 bucks... Max.... And I always have happy customers...</p>